feat: timeline multi-select, demand popover, resource hover card, merged tooltips, dark mode fixes

Major timeline enhancements:
- Right-click drag multi-selection with floating action bar (batch delete/assign)
- DemandPopover for demand strip details (replaces broken "Loading" modal)
- ResourceHoverCard on name hover showing skills, rates, role, chapter
- Merged heatmap+vacation tooltips into unified TimelineTooltip component
- Fixed overbooking blink animation (date normalization, z-index ordering)
- Fixed dark mode sticky column bleed-through in project view
- System roles admin page, notification task management, performance review docs

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/app/(app)/resources/ResourcesClient.tsx

@@ -1296,7 +1296,7 @@ export function ResourcesClient() {
                                   {skills.slice(0, 3).map((s) => (
                                     <span
                                       key={s.skill}
-                                      className="inline-block rounded-full bg-brand-50 px-2 py-0.5 text-xs text-brand-700 dark:bg-brand-950/30 dark:text-brand-200"
+                                      className="inline-block rounded-full bg-brand-50 px-2 py-0.5 text-xs text-brand-700 dark:bg-brand-900/60 dark:text-brand-100"
                                     >
                                       {s.skill}
                                     </span>